Posted: 10/05/2015 at 19:22
No of course you're not too old. I'm 51 and started running in my forties.
All I would add is - have some shorter term goals. Everyone wants to run a marathon as soon as they start running but it's a massive undertaking for most people. Have you got a local parkrun? Follow a couch to 5k plan with a view to doing your first 5k parkrun (google it) in say 8 weeks or so. It feels like a real milestone when you get to running 5k/30 minutes non stop when you first start out.
Build slowly from there, 10ks maybe or up to half marathon. If you get into London go for it, if not make a 10k or half your goal, maybe a big flashy race which will be fun to be part of. Make running part of your life, if you set the bar too high you simply won't keep it up.
Most of all stop smoking.